Carboxyvinyl polymers or alkyl modified carboxyvinyl polymers and other ionic water-soluble polymer compounds produce increased viscosity by repulsion between ions, so it is possible to obtain high viscosity using even a small quantity thereof. It is therefore possible by using an ionic water-soluble polymer compound as a thickening agent to set a wide range of viscosities while minimizing the stickiness or slipperiness that is specific to a polymer, and also to impart a succulent and fresh feel to the consumer by using the thixotropy specific to the ionic water-soluble polymer compounds.
Ionic water-soluble polymer compounds are therefore widely used as a cosmetic starting material; particularly, as a water-phase thickening agent for water-based cosmetics, oil-in-water emulsified cosmetics, and the like.
Whereas an ionic water-soluble polymer compound has excellent characteristics as a thickening agent, cases are also identified in which it is difficult to appropriately control the viscosity of an added composition because of interaction due to contact with ionic groups of other ingredients or other ionic substances.
For example, because the surfaces of particles of titanium oxide powder generally used as a pigment are usually modified with alumina, zinc oxide, or the like, when the powder is added to a water phase that has been thickened with an ionic water-soluble polymer compound, ions derived from the modifying agent interact with the ionic water-soluble polymer compound, whereby general or localized reductions or increases in viscosity occur, the powder particles aggregate, and other effects are encountered, and it is difficult to provide a succulent feel from the natural thickening effect produced by the ionic water-soluble polymer compound and to obtain the effects produced by the titanium oxide powder while maintaining the stability of the composition.
In order to overcome these drawbacks, attempts have been made to control the interaction between ions by performing fluorine treatment or another hydrophobization treatment on titanium oxide or other powder particles (for example, see Japanese Laid-open Patent Application No. 9-143023, 7-112915, or 9-143031), but even when hydrophobized powder particles are dispersed in an oil phase in the process of manufacturing an oil-in-water emulsified composition, elution of ions into the water phase over time cannot be completely minimized, so it has been difficult to obtain a composition having adequately good stability.
Polysaccharides or derivatives thereof, for example, are also used as water-soluble polymer compounds that are not affected by ions originating from the added substance, but the added quantity thereof must be increased in order for a certain degree of viscosity to be retained by these water-soluble polymer compounds. Therefore, when only a small quantity of the polysaccharide or the like is used, the composition being added to is limited to an extremely low viscosity, and when a large quantity of the polysaccharide or the like is admixed therein in order to obtain a high viscosity, slipperiness, stickiness, and also runniness of the polymer and other effects occur, and it is difficult to provide an additive-containing composition having good tactile properties.
An object of the present invention is to provide a means for demonstrating a succulent feel originating from the increased viscosity induced by the ionic water-soluble polymer compound, and the effects intrinsic to the powder particles with stability over time, in an oil-in-water emulsified composition that uses an ionic water-soluble polymer compound, to which composition the powder particles are added.